Semiconductor devices include metal layers that are insulated from each other by dielectric layers. As device features shrink, reducing the distance between the metal layers, capacitance increases. To address this problem, insulating materials that have a relatively low dielectric constant (herein referred to as low-k dielectrics) are being used in place of silicon dioxide (and other materials that have a relatively high dielectric constant) to form the dielectric layer that separates the metal lines.
A material that may be used to form such a low-k dielectric layer is carbon doped oxide, which can be deposited using standard PECVD equipment. (Copending applications, Ser. Nos. 09/422,841 and 09/465,654, filed Oct. 21, 1999 and Dec. 17, 1999 respectively, each assigned to this application's assignee, describe semiconductor devices that include a carbon doped oxide dielectric layer.) Using this material instead of silicon dioxide to separate metal lines may yield a device having reduced propagation delay, cross-talk noise and power dissipation. Although carbon doped oxide is a promising low-k substitute for silicon dioxide, films formed from this material may be relatively brittle. As a consequence, such films' crack resistance may be poor. In addition, such films may suffer from unacceptable flaking and are prone to delamination. As a result, use of such brittle low-k films may be restricted to forming layers having a thickness that is well below their cracking threshold—perhaps limiting their use to forming films that are less than about 1 micron thick.
Accordingly, there is a need for a semiconductor device, which includes a low-k dielectric layer (e.g., one including a carbon doped oxide) that is less susceptible to cracking. There is also a need for an improved process for making such a semiconductor device. The present invention provides such a semiconductor device and a process for making it.